Police in Kuwait have arrested five Islamic State suspects, including an 18-year-old man planning to attack a Shiite mosque, in the final days of the Muslim fasting month of Ramadan.

The man, a Kuwaiti, confessed to plotting the attack and had planned to deploy a suicide vest, the Interior Ministry said.

An IS attack against a Shiite mosque in Kuwait in June last year killed at least 27 people.

Police also detained a 52-year-old mother and her son accused of helping IS fighters in Syria, where the group holds territory, and two other Kuwaitis who possessed assault rifles and the black IS flag.